I came across this site a few years ago. Free to all with no login, they allow you to search for any call sign and show it on a map, complete with path from originating airport.
They have a free account allowing you to do even more (single plane) and 25 planes will cost you US$40/year. Android and iOS apps available.
They also have information on how to get or build the necessary equipment.
The most recent information I can get with a simple Google search shows that the call sign of one of her planes is N621MM, although other links suggested that she has more than one plane and has sold planes to escape this tracking.
BinJuice